Amid the Belmont Stakes, the NBA Finals, the Stanley Cup, next week's U.S. Open golf and that quaint little soccer tournament starting up in Brazil next week, tennis might not even make the list of things you'll DVR and then forget to watch later.

But this Sunday at 9 a.m. ET on NBC, do yourself a favor and watch the French Open final between Rafael Nadal and Novak Djokovic—the next act of the greatest current rivalry in sports.

Nadal, the 28-year-old lefty from Spain and the best player in history on clay, has won this title eight times and lost just one match in Paris. This will be his ninth final. His forehand has so much spin that it drops and curves sideways and saps the spirit of everyone who plays against it.

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That is, almost everyone. Djokovic, 27, knows Nadal like no one else knows him. This will be their 42nd meeting, more than any two players since 1968, when the Open era of tennis began. So far Nadal has won 22, Djokovic 19. Djokovic has won the last four. He beat Nadal on clay this spring, in Rome. At last year's French Open, in the semifinals, Djokovic came oh-so-close: Nadal won 9-7 in the fifth set.

This is the only one of the four Grand Slam tournaments that Djokovic has yet to win. Nadal has won them all. Roger Federer has won them all. They are part of a small club—only seven men have done it in the history of tennis—and Djokovic wants in. An added bonus: If Djokovic wins the final on Sunday, he'll be the No. 1 player in the world and Nadal will drop to No. 2.

For most of this tournament, Djokovic looked untouchable. Efficiency is his trademark. Compact swings. Elegant slides. No step wasted. Few mistakes. He was humming along until Friday's semifinal against Ernests Gulbis, a wild-haired ball smasher who had upset Federer earlier in the tournament.

For two sets, Djokovic looked good. Then not so much. He smashed a racket. He lost a set. He breathed heavily. When he spoke afterward, he sounded like he had a cold.

"All his hopes make him a little more tense than usually," said Marian Vajda, who coaches Djokovic alongside tennis legend Boris Becker.

"I'm trying to channel this energy into the right direction and not get carried away too much by the stress of the occasion," Djokovic said.

Nadal has been tougher to read. He zipped through an easy draw until the quarterfinals, and then suddenly looked lost. Weak serve. Terrible backhand. His opponent, David Ferrer, fell apart and Nadal moved on, but everyone wondered about his achy back, which hurt him in the Australian Open final (Nadal lost to Stanislas Wawrinka). Nadal said he felt good in practice. He looked confused as to why he wasn't so good when it counted.

His uncle and coach, Toni Nadal, said the match was "one of the best that he has ever played here"—high praise from a man who has seen his nephew go 89-1 in his career in best-of-five-set clay court matches.

Nadal's forehand is solar powered. In the heat, the ball moves faster, bounces higher, stings with more force: "I am able to create more with less," he said. So far, the forecast for Sunday calls for warm temperatures again, but maybe some showers.

Uncle Toni, who has coached Nadal since he was a child, offered his typically understated take on what will transpire.

"The match will be very difficult," he said. "Difficult for us—and I think difficult for Djokovic too."

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